Infuse the Cream: In a medium saucepan, combine the heavy cream and rosemary sprigs. Heat over medium heat, stirring occasionally, until it just begins to simmer. Remove from heat, cover, and let it steep for 30 minutes.

Preheat and Prep: Preheat your oven to 325°F (160°C). Place six ramekins in a large baking dish.

Whisk Egg Yolks and Sugar: In a mixing bowl, whisk together the egg yolks and 1/2 cup of granulated sugar until pale and slightly thickened.

Temper the Eggs: Remove the rosemary sprigs from the infused cream. Slowly pour the warm cream into the egg yolk mixture, whisking constantly. Stir in the vanilla extract.

Strain the Custard: Pour the custard mixture through a fine-mesh sieve into a pitcher or large measuring cup.

Fill the Ramekins: Carefully pour the strained custard into the prepared ramekins, dividing it evenly.

Create the Water Bath: Pour hot water into the baking dish, around the ramekins, until it reaches halfway up the sides of the ramekins.

Bake the Custards: Bake for 30-40 minutes, or until the custards are set around the edges but still slightly jiggly in the center.

Cool and Chill: Let the ramekins cool in the water bath for about 30 minutes, then remove them and let them cool completely at room temperature. Cover and refrigerate for at least 2 hours.

Caramelize the Sugar: Just before serving, sprinkle a thin, even layer of granulated sugar over the top of each chilled custard. Use a kitchen torch to caramelize the sugar until golden brown and hardened.